This invention relates to improved optical waveguide devices capable of being coupled with each other through matching slots on each device. The incorporation of a mirror or a partially reflective surface within the device facilitates cascading the device with other waveguide structures to form an optical bus structure. The instant invention also relates to methods of making such optical devices.
Optical communication systems offer several advantages over other wire-based communication systems for transmitting messages. These advantages include greatly increased bandwidth and channel capacity of communication and the ability to use lower cost, smaller, lighter weight materials compared to large, heavy, expensive copper cables.
As the development of optical circuits proceeded, it became necessary to have optical waveguide devices which could couple, divide, switch and modulate the optical waves from one optical fiber to another, or from one waveguide device to another. For example devices see U.S. Pat. Nos. 3,689,264, 4,609,252 and 4,637,681.
Connecting optical devices to one another has traditionally been a problem. One method is to fuse or melt fibers or other waveguide configurations, for example, together so that light from one fiber or waveguide can pass to the connected fibers or waveguides. However, in such a fusion process it is difficult to control the extent of fusion and the exact geometry and reproducibility of the final structure. Significant loss of signal can result.
U.S. Pat. No. 5,292,620 teaches a method of fabricating buried waveguides in a laminated multi-layered polymer structure, the disclosure of which is incorporated herein by reference. U.S. Pat. No. 5,394,495 discloses optical waveguide connectors for coupling light signals between multiple waveguides in one or more stacked planar multilayer polymer waveguide structures using the fabrication method of U.S. Pat. No. 5,292,620.
U.S. Pat. No. 5,062,681 utilizes matching slots, symmetrically disposed around waveguides formed in a generally planar multilayer polymer structure to precisely couple waveguides to optical devices, the disclosure of which is also incorporated herein by reference.
The instant invention is directed to improved optical waveguide devices of the type capable of being coupled with each other through matching slots on each device. In each embodiment of the present invention the optical waveguide device preferably comprises a laminate of a middle photopolymer layer containing a waveguide, and at least one pair of external photopolymer layers each having the same thickness.
A first embodiment comprises a twisted multi-ribbon waveguide connector assembly having slots for connection to a corresponding slotted waveguide device. In the first embodiment multiple parallel waveguides are formed in a laminated multi-layer planar structure and slots are ablated symmetrically about one end of each waveguide. The multi-layer planar waveguide structure is then slit into individual ribbons in the vicinity of the slotted ends to form a first group of ribbons, so that each ribbon contains at least one waveguide. The slotted end of each ribbon is then twisted ninety degrees and inserted into a cavity in a housing, such that each slotted end protrudes out of the housing, to form an optical connector. Each ribbon is attached to the housing by suitable attachment means. A photo-curable adhesive or a molding resin is preferably injected into the cavity of the housing and cured. Alternatively, the housing may be configured to clamp the slotted ends of the ribbons in place in the housing. The spacing of the slotted ends in the connector is chosen to match the spacing of corresponding slotted waveguide ends in a second connector having a group of waveguides that are arranged in a generally planar array. The slotted ends of the first group of waveguides in the optical connector may then be joined to the corresponding slotted ends of waveguides of the second group. The corresponding slotted ends facilitate the alignment of the waveguides of the first group with the waveguides of the second group.
More particularly, this first embodiment of the invention pertains to a first slotted optical waveguide device comprising an interior portion and a first plurality of exterior ribbon portions, each ribbon having a central axis therethrough and containing a waveguide along the ribbon axis, the ribbon being adaptable to be connected to a second slotted optical waveguide device, each ribbon portion of the first device comprising: a terminal edge; a first pair of opposite external surfaces, substantially parallel to each other, and extending away from the terminal edge; and a waveguide positioned equidistantly between the first pair of the opposite external surfaces, the waveguide having an end point and a center axis, the center axis coinciding with the central axis of the ribbon, the center axis forming a substantially right angle to the terminal edge; the ribbon also having a thickness, and a through-slot extending in a direction substantially parallel to the direction of the waveguide, the through-slot starting at the terminal edge and extending adequately within the ribbon as to meet the end of the waveguide, the through-slot having a width, and a center axis coinciding with the center axis of the waveguide, the through-slot confined by a second pair of opposite side surfaces, substantially parallel to each other and to the center axis of the waveguide, and substantially perpendicular to the first pair of surfaces with the requirement that the width of the through-slot is not excessively smaller than the thickness of the second matching optical waveguide device; and an internal surface meeting with and being substantially perpendicular to the first and the second pairs of surfaces, the internal surface having a center point, the center point coinciding with the end of the waveguide, the terminal edge end of the ribbon being twisted substantially ninety degrees from the interior portion so that when the through-slot of the optical waveguide device is coupled with a similar slot of the second device, wherein the slots of the second device lie in a common plane (i.e., not twisted), the ends of the respective waveguides come in contact, and the center axes of the waveguides substantially coincide.
Preferably, the width of the through-slot is adequately smaller than the thickness of the device, so that when the optical waveguide device is connected to a similar device through coupling of their respective through-slots, a tight and secure fit is created.
A second embodiment of the waveguide device of the present invention is a waveguide connector assembly, arranged for coupling both to a second waveguide device and to a third waveguide device. In the second embodiment a waveguide is formed in a laminated multi-layer planar structure which is generally rectangular in shape, the waveguide being comprising a first segment and a second segment, the first and second segments being disposed substantially orthogonal to each other.
The first waveguide segment has a first terminal end and a second interior end, the second segment has a first terminal end and a second interior end. A central mirror is positioned so that light from the interior end of the first waveguide segment is reflected into interior end of the second waveguide segment. A slot cavity is formed in a central region of the device, preferably by ablation, the cavity being positioned so that a first planar surface of the cavity intersects each of the two waveguide segments at an acute angle, preferably at about a forty five degree angle. A mirror may be inserted into the cavity at the surface of the cavity that intersects the waveguides. Alternatively the surface of the cavity that intersects the waveguides may be coated with a suitable material to form a mirror. Each terminal end of the waveguide segments is slotted, the slotted ends being disposed substantially orthogonal to each other.
The slotted end of the first waveguide segment in the waveguide device may then be joined to a corresponding slotted end of a respective waveguide in a second slotted waveguide device and the slotted end of the second waveguide segment in the wavegiude device may then be joined to a corresponding slotted end of a respective waveguide in a third slotted waveguide device.
A third embodiment of the waveguide device of the present invention is suitable for coupling to a second waveguide device, to a third waveguide device, and to a fourth waveguide device. In the third embodiment a branched three segment waveguide is formed in a multi-layer planar structure, generally rectangular in shape, the waveguide comprising a first segment having a first terminal end and a second interior end, a second segment having a first terminal end and a second interior end, a third segment having a first terminal end and a second interior end. A partially reflecting central mirror is positioned to receive light from the first segment so that part of the light from the first waveguide segment is reflected by the mirror into the second waveguide segment and part of the light from the first waveguide segment passes through the mirror into the third waveguide segment. A slot cavity is formed in a central region of the device, preferably by ablation, the cavity being positioned so that one surface of the cavity intersects each of the interior ends of the three waveguide segments at an acute angle, preferably at about a forty five degree angle. A partially reflecting mirror may be inserted into the cavity at the surface of the cavity that intersects the waveguides.
Alternatively the surface of the cavity that intersects the waveguides may be coated with a suitable material to form the partially reflecting mirror surface. Each terminal end of the three waveguide segments are slotted, the slotted ends of the first waveguide segment and third waveguide segment each being disposed substantially orthogonal to the second waveguide segment.
A fourth embodiment of the waveguide device of the present invention is suitable for coupling to a second waveguide device, to a third waveguide device, and to a fourth waveguide device and switching light from the second waveguide device to the third waveguide device or to the fourth waveguide device. In the fourth embodiment a branched three segment waveguide is formed in a multi-layer planar structure, generally rectangular in shape, the waveguide comprising a first waveguide segment having a first terminal end and a second interior end, a second waveguide segment having a first terminal end and a second interior end, and a third waveguide segment having a first terminal end and a second interior end.
A reflecting central mirror, movable between a first position and a second position, is positioned in a central slot cavity to receive light from the first segment. When the central mirror is in the first position the light from the first waveguide segment is reflected by the mirror into the second waveguide segment. When the central mirror is in the second position the light from the first waveguide segment passes by the mirror into the third waveguide segment. A slot cavity is formed in a central region of the device, preferably by ablation, the cavity being positioned so that one surface of the cavity intersects each of the interior ends of the three waveguide segments at an acute angle, preferably at about a forty five degree angle. The mirror may be inserted into the cavity at the surface of the cavity that intersects the waveguides and may be moved by any suitable means.
Alternatively the cavity that intersects the waveguides may be partially filled with a suitable liquid material to form the reflecting mirror surface, such that an air bubble remains in the cavity. Each terminal end of the three waveguide segments are slotted, the slotted ends of the first waveguide segment and third waveguide segment each being disposed substantially orthogonal to the second waveguide segment.
The instant invention also relates to methods of making such optical devices. More particularly it pertains to a first method of coupling two optical waveguide devices, a second method of coupling two optical waveguide devices and a third method of coupling three optical waveguide devices. In the first method each optical device having a terminal edge, a first pair of opposite surfaces substantially parallel to each other, and a waveguide positioned equidistantly between the opposite surfaces, the waveguide having a center axis forming a substantially right angle with the terminal edge, comprising the steps of: forming a through-slot in a direction substantially parallel to the direction of the waveguide, the through-slot starting at the terminal edge of each device and extending adequately within the device to remove at least part of the waveguide and form an end on the waveguide, in a way that the through-slot has a center axis coinciding with the center axis of the waveguide, and a second pair of opposite side surfaces, substantially parallel to each other and to the center axis of the waveguide, and substantially perpendicular to the first pair of surfaces with the requirement that the width of the through-slot is not excessively smaller than the thickness of the device, and an internal surface meeting with and being perpendicular to the second pair of surfaces, the internal surface having a center point, the center point coinciding with the end of the waveguide, slitting the multilayer waveguide structure into ribbons, twisting the ribbons substantially ninety degrees, and inserting the slotted ends into a housing. The slotted end of one device is inserted into a similar slot of a second device in a way that the ends of the respective waveguides come in contact, and the center axes of the waveguides substantially coincide. When a permanent connection of two waveguide devices is desired it is preferable to adhere the respective waveguide ends of the two devices to each other with an adhesive photopolymer composition.